1. Field of the Invention
The present invention relates to a thin film magnetic head comprising at least an inductive magnetic transducer for recording, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in the areal density of a magnetic recording medium (hereinafter simply referred to as “recording medium”) such as a hard disk or the like. As magnetic recording systems applicable to the thin film magnetic head, for example, a longitudinal recording system in which a signal magnetic field is oriented in an in-plane direction (a longitudinal direction) of a recoding medium and a perpendicular recording system in which the signal magnetic field is oriented in a direction perpendicular to a surface of the recording medium are well known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, it is assumed that the perpendicular recording system instead of the longitudinal recording system holds promise for future, because the perpendicular recording system can obtain such an advantage that higher liner recording density can be achieved, and a recording medium in which data has been already recorded has resistance to thermal decay effects.
As recording modes using the perpendicular recording system, for example, (1) a mode using a head (ring type head) facing each other with a gap in between on an end side and being magnetically coupled to each other on the other end side and a recording medium having a single-layer structure as a main part, and (2) a mode using a head (single-pole type head) being disposed perpendicular to a recording medium and a recording medium having a two-layer structure as a main part have been proposed. In these modes, the mode using a combination of the single-pole type head and the recording medium having the two-layer structure becomes a focus of attention as a mode which can improve the performance of the thin film magnetic head, because the mode has remarkably superior resistance to thermal decay.
As the single-pole type thin film magnetic head using the perpendicular recording system, for example, a thin film magnetic head with a structure in which on a yoke layer disposed so that a thin film coil is covered with the yoke layer, a pole layer is disposed so as to be connected to the yoke layer is well known. The thin film coil generates magnetic flux for recording, and has a winding structure in which the thin film coil is wound around an end portion (back gap) of the yoke layer on a side farther from an air bearing surface. In the thin film magnetic head, when the magnetic flux is generated in the thin film coil, after the magnetic flux flows into the pole layer through the yoke layer, the magnetic flux is emitted from an end of the pole layer to outside. A magnetic field (perpendicular magnetic field) for recording is generated by the emitted magnetic flux, and a surface of the recording medium is selectively magnetized by the perpendicular magnetic field, so information is magnetically recorded on the recording medium.
In order to secure stable and high recording performance in the perpendicular recording system thin film magnetic head, for example, it is required to appropriately control the flow of magnetic flux from the yoke layer to the pole layer so as to prevent an excessive amount of the magnetic flux from being supplied to an end of the pole layer. It is because when the excessive amount of the magnetic flux is supplied to the end of the pole layer, thereby an unnecessary magnetic flux is emitted from a portion of the pole layer except for the end, that is, a portion around the end from which the magnetic flux should not be emitted to outside, due to a magnetic field (leakage magnetic flux) generated by the unnecessary magnetic flux, information which has been already recorded on the recording medium may be overwritten without intension.
However, in a conventional perpendicular recording system thin film magnetic head, when the flow of the magnetic flux from the yoke layer to the pole layer is not appropriately controlled, for example, depending upon conditions such as an amount of magnetic flux generated in the thin film coil, or the like, information may be overwritten without intention due to the leakage magnetic field. Such a problem exerts a large influence on reliability of the thin film magnetic head, so it is required to take immediate measures against the problem.
As in the case of the invention, some thin film magnetic heads have been already known as the thin film magnetic head for the purpose of securing stable and high recording performance.
More specifically, for example, as a thin film magnetic head capable of securing high frequency recording performance, a thin film magnetic head comprising a first magnetic member having a laminate structure in which a layer on a side closer to a write gap layer is made of a high saturation magnetic flux density material, a second magnetic member having a laminate structure in which a layer on a side closer to the write gap layer is made of a high saturation magnetic flux density material, and a third magnetic member constituting a magnetic circuit together with the first and the second magnetic members, and having a laminate structure in which an outer magnetic film is made of a high-permeability material, and an inner magnetic film is made of a high resistivity material is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-297409). Moreover, as a thin film magnetic head capable of securing high frequency characteristics, a thin film magnetic head comprising a bottom core layer, a write gap layer, and a top core layer including a top first magnetic layer and a top second magnetic layer, and having a structure capable of processing the dimension of a track width with high precision and capable of reducing the generation of an eddy current by the shape of a connecting region between the top first and second magnetic layers is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-8209). However, these thin film magnetic heads use the longitudinal recording system, and it is not certain whether the thin film magnetic heads can control the flow of magnetic flux in a top core layer so as to prevent information from being overwritten without intention.
Further, for example, as a perpendicular recording system thin film magnetic head capable of improving efficiency of passing magnetic flux from a yoke layer to a main pole layer, a thin film magnetic head having a structure in which a main pole layer is disposed on a inclined or curved front end surface of the yoke layer is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-197611). In the thin film magnetic head, the main pole layer can be appropriately plated in a predetermined shape, and the efficiency of passing the magnetic flux from the yoke layer to the main pole layer can be improved. However, in the thin film magnetic head, by improving the efficiency of passing the magnetic flux from the yoke layer to the main pole layer, the flow of magnetic flux is controlled in order to reduce the leakage of the magnetic flux from the yoke layer to outside. Therefore, in the thin film magnetic head, the flow of the magnetic flux is not controlled in order to reduce the leakage of the magnetic flux from a portion around an end of the main pole layer to outside.
Moreover, for example, as a perpendicular recording system thin film magnetic head capable of improving signal quality of a reproducing waveform, a thin film magnetic head comprising a main pole, a coil for excitation and a return yoke of which a portion facing the main pole is cut away is known (for example, refer to Japanese Unexamined Patent Application Publication No. Hei 6-180810). However, it is not certain whether the thin film magnetic head can control the flow of the magnetic flux in the main pole so as to prevent information from being overwritten without intention.
For example, as a perpendicular recording system thin film magnetic head capable of appropriately guiding magnetic flux induced from a coil layer to an end surface of a main pole layer, a thin film magnetic head comprising an auxiliary pole layer, a main pole layer disposed on a flat insulating layer, and a yoke layer disposed on the main pole layer, and having a structure in which the width of a front end surface of the main pole layer gradually increases in a track width direction with distance from the auxiliary pole layer is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-197615). However, it is not certain whether the thin film magnetic head can control the flow of the magnetic flux in the main pole layer so as to prevent information from being overwritten without intention.